Field of the Invention
The present invention relates to a process for determining the optimal richness of a fuel-air mixture supplied to an internal combustion engine and a corresponding device. More particularly, this device is intended for use with engines of the type used in pumps, generator sets, lawn mowers, etc.
Engines of the above-mentioned type generally run at a constant speed, regardless of the load on the engine. Their carburetion system must therefore supply them with appropriate amounts of air and fuel, no matter what the load is on the engine.
Due to environmental concerns, it has become necessary to impose pollution emission standards for these small internal combustion engines, as is already the case for automobile engines.
In order to reduce the pollution from an engine, it is imperative to burn the fuel as completely as possible during the combustion phase of the fuel mixture. It is therefore advantageous to determine the optimal fuel and air mixture (that is, the optimal richness of the mixture), thus allowing complete combustion. When the engine is thus supplied with a mixture having the optimal richness, it is noted that the torque delivered by the engine is also optimal, as is the rotational speed of the engine. To verify that an engine is operating at the optimal richness, one need only determine the fuel-air mixture that provides the maximal rotational speed of the engine.
Unfortunately in the case of lawn mowers, generator sets, etc., the engine is equipped with a speed regulator in order to have a constant rotational speed. For engines of this type which have a speed regulator, the monitoring of the engine speed is not indicative of the torque and the optimal richness. Therefore, the monitoring of another engine parameter is necessary. However, this monitoring must use the lowest possible number of sensors in order not to increase the cost of the engine.